1. Field of the Invention
This invention relates to a single lens reflex camera system which is capable of TTL flash output control of a flash unit.
2. Description of the Prior Art
Recently, the so-called TTL flash output control system has been widely carried out in flash photography. This TTL flash output control system is such that the flashlight emitted from a flash unit and reflected by an object and passed through the lens of the camera and reflected by the film surface of the camera is received by a light-receiving device within the camera and the light emission of the flash unit is stopped on the basis of the metering output of the light-receiving element of the light-receiving device. Single lens reflex cameras are known in which during flash photography, the above-described TTL flash output control is effected and during ordinary photography, automatic exposure control is effected on the basis of the TTL metering value while, at the same time, a proper shutter time and a proper exposure value such as a proper aperture value which are to be automatically controlled are displayed. In the single lens reflex cameras of this type, the light-receiving device is disposed on the underside of the mirror box of the camera to receive the reflected light from the film during TTL flash output control. Accordingly, when the quick return mirror is in an observation position, namely, a position in which the light passed through the objective lens is reflected to the viewfinder system, the light passed through the objective lens does not impinge on the light-receiving device and therefore, another light-receiving device becomes necessary to obtain a metering output for displaying a proper exposure value and said another light-receiving device is disposed within the viewfinder system. However, such provision of two light-receiving devices in the camera results in an increased cost and also aggravates the availability of the space within the camera, and further leads to a disadvantage that the regulation for correctly displaying the exposure information and the regulation for correctly effecting the exposure control become entirely independent of each other and thus, the regulations require much time and it is very difficult to make the characteristics of the two regulations coincident with each other.